Mary Barker is Professor of Psychology and Behavioural Science. She has a joint appointment in both the Faculty of Medicine and the School of Health Sciences, Faculty of Environmental and Life Sciences, University of Southampton UK. Mary runs a programme of work in both the UK and in low-income countries aiming to engage young people in improving their sense of agency, well-being and mental health, to benefit their health in general but their diets and physical activity habits more specifically. Her team’s approach is participatory and combines social activism focused on engaging young people in the climate change and health agenda and testing methods of one-to-one support and digital resources including smartphone games. Much of this work takes place as part of her NIHR Programme Grant for Applied Research EACH-B (Engaging Adolescents in Changing Behaviour). She partners in this activity with the TALENT network of colleagues with interests in adolescent health and well-being based in institutions in low-and-middle-income countries. Her team also ran a five-country, longitudinal qualitative study with young people throughout the pandemic exploring their experience, mental health, well-being and resilience, data from which supported UK local and national government COVID messaging to young people. She is adjunct professor at the University of Agder, Norway, and has honorary appointments at the University of Witwatersrand, South Africa, and University College London.